1. Technical Field of the Invention
The present invention relates to brushless automotive alternators for use in, for example, trucks, construction machines, and agricultural machines.
2. Description of the Related Art
Automotive alternators are generally classified into two types. The first type is brushed type for passenger cars; the other is brushless type for trucks, which are generally required to travel long distances, and construction and agricultural machines which are generally required to operate under severe conditions (e.g., dusty conditions).
In particular, for a brushless automotive alternator used in a long-distance truck or a construction machine, a “one wire-charging system” is generally used for the purpose of minimizing the total length of necessary wires.
More specifically, in the one wire-charging system, as shown in FIG. 5, the brushless alternator 300 includes an output terminal B that is connected, via a single wire, to the plus (+) terminal of a battery 200 for charging it; at the same time, the brushless alternator 300 is grounded via a housing of the alternator 300.
Moreover, when the brushless alternator 300 further includes an indicator light terminal I, as shown in FIG. 5, the system is referred to as “one wire-charging system with terminal I” or “two-wire system”. The terminal I is electrically connected, as shown in FIG. 6, between an auxiliary diode-trio 65 of the alternator 300 and an indicator light 150 on the vehicle, so as to drive the indicator light 150 with the electric power output from the auxiliary diode-trio 65.
The brushless alternator 300 further includes, as shown in FIGS. 5 and 6, a relay terminal R for outputting the electric power generated by one of the three different-phase stator windings of the alternator 300. The electric power output via the relay terminal R is used for various indicators, a tachometer, and an hour meter on the vehicle.
Conventionally, both the indicator light terminal I and the relay terminal R are made of a conductive metal plate, and directly connected to the auxiliary diode-trio 65 and the one of the stator windings, respectively.
Furthermore, as shown in FIG. 7, a fuse F is generally provided on the vehicle side (i.e., the opposite side to the terminal I with respect to the indicator light 150). When a vehicle-side wire connected to the terminal I is short-circuited with, for example, the vehicle body or an engine bracket, the fuse F will blow, thereby protecting the indicator light 150 and the alternator 300 from electrical damage.
However, referring back to FIG. 6, when conductive foreign matters accidently enter the inside of the alternator 300 to cause a short circuit between the terminals R and B, or when wires connected to the terminals R and B are short-circuited together outside the alternator 300 due to engine vibrations, electrical damage to the components of the alternator 300, such as the stator windings and diodes, is inevitable.
To solve the above problem, one may consider connecting one of the stator windings to the relay terminal R via an IC regulator 7 and configuring the IC regulator 7 to have a function of protecting the components of the alternator 300 from electrical damage in the above-described cases. However, this will require a redesign of the IC regulator 7 and thus considerably increase the manufacturing cost of the alternator 300.
In addition, as a related prior art, U.S. Pat. No. 5,681,495 discloses an automotive alternator for use in a passenger car, wherein the electric power generated by one of the three different-phase stator windings of the alternator is output via a multifunctional controller (or IC regulator). With this configuration, when a wire carrying the electric power generated by the one of the stator windings is short-circuited with, for example, the car body, the controller functions to protect the components of the alternator from electric damage.